1. Field of the Invention
The present invention relates to ink-jet printers and, more particularly to a carriage for an ink cartridge as a source of supply of ink to an ink-jet printhead.
2. Description of the Related Art
Ink-jet printers print by shooting drops of ink onto a page. The ink is stored in an ink cartridge and discharged onto the page through an ink-jet printhead. The ink cartridge and printhead are housed in a carriage that can move reciprocally across the page. To print an image, the printhead moves back and Forth across the page shooting drops as it moves.
JP-A7-246716 discloses an ink-jet printer wherein an ink cartridge and an ink-jet printhead are housed in a carriage. The cartridge has a rack. The carriage includes a base, a case fixed to the base, a pinion lever and a lock lever. The base supports the printhead. The lock lever and the pinion lever are pivoted to a pivot support that is fixedly attached to the case. At one end portion, the lock lever has a lock lever axis that is disposed in the neighborhood of an upper edge of the case At the opposite end portion, the lock lever has a knob including a hook adapted to engage a predetermined portion of the upper edge of the case. At an intermediate portion between the lock lever axis and the knob, the lock lever is formed with a protrusion adapted to contact with a top face of the cartridge. The pinion lever includes a pinion. The pinion has a pinion axis, about which the pinion lever pivots. The pinion axis is so arranged as to cause the pinion to engage the rack upon insertion of the cartridge into the case. The pinion lever has a pin cooperating with a groove of the lock lever for conjoint operation therewith. A spring biases the pinion lever in such a direction as to separate the pin from the groove of the lock lever, causing the pinion to lift the cartridge towards an elevated position from the upper edge of the case. Replacement of an old cartridge with a new one is initiated by manipulating the knob to disengage the hook from the upper edge of the case and turning the lock lever in an unlocking direction about the axis. This causes the pinion lever to turn the pinion to lift the cartridge to the elevated position. In this elevated position, the old cartridge is removed easily from the case for replacement with a new one. The new cartridge is inserted into the case with its rack engaging the pinion and held in the elevated position due to the spring of the pinion lever. Then, the lock lever is turned in a locking direction, opposite to the unlocking direction, causing the protrusion to lower the cartridge against the spring to an operative position. This turning motion of the lock lever in the locking direction is completed upon engagement of the hook with the upper edge of the case.
FIG. 4 illustrates in section a less preferred example of a carriage, generally designated by the reference numeral 1, of an ink-jet printer. The carriage 1 houses an ink-jet printhead 2 and an ink cartridge 3. A guide rod 7 supports the carriage 1 for reciprocal back and forth motion across a page. A lock lever 4 is provided to lock the cartridge 3 to an operative position within the carriage 1. At one end portion, the lock lever 4 is pivotally supported via a rotary shaft 4a by a shaft-supporting portion 1a of the carriage 1. At the opposite end portion, the lock lever 4 is provided with a downwardly extending knob 4b. At a leading end portion, the knob 4b is curled inwardly to define a hook 4c. The hook 4c is elastic enough to engage, in a snap fit manner, a lateral projection on a sidewall of the carriage 1. At an intermediate portion between the one and the opposite end portion, the lock lever 4 is formed with a protrusion 4d. In FIG. 4, the fully drawn line shows the lock lever 4 in a position to close an opening of the carriage 1. In this position, the protrusion 4d presses the cartridge 3 on a top face thereof into a locked state. At a bottom face, the cartridge 3 is provided with an ink supply port 5. At a position opposed to the ink supply port 5, an elastic cap 6 is arranged on the printhead 2.
Replacement of cartridge with a new one is initiated by manipulating the knob 4b to disengage the hook 4c from the lateral projection 1b of the carriage 1 and turning the lock lever in an unlocking direction, clockwise viewing in FIG. 4, about the axis of the rotary shaft 4a. This uncovers the cartridge 3, allowing replacement with a new one. The new cartridge is inserted into the carriage 1. Then, the lock lever 4 is turned in a locking direction, opposite to the unlocking direction, causing the protrusion 4d to lower the cartridge 3, compressing the elastic cap 6, to an operative position. This turning motion of the lock lever 4 in the locking direction is completed upon frictional engagement of the hook 4b with the lateral projection 1b of the carriage 1.
The elastic cap 6 is compressed to firmly engage the bottom face of the cartridge 3 to define and seal a cavity around the ink supply port 5. The reaction force of the compression of the elastic cap 6 acts on the lock lever 4 via the interface between the top face of the cartridge 3 and the protrusion 4d. As the hook 4c and the rotary shaft 4a engage the edge 1b and the shaft-supporting portion 1a, respectively, the edge 1b and the shaft-supporting portion 1a bear all stress that the lock lever 4 is subjected to. At the interface between the hook 4b and the edge 1b of the carriage 1, a component of the reaction force acts on the edge 1b in a direction normal thereto, producing resistance to be overcome in disengaging the hook 4c from the lateral projection 1b. A problem with structure is that if the elastic cap 6 is compressed sufficiently to provide an effective seal around the ink supply port 5, effort required to disengage the hook 4b from the edge 1b may increase to an unacceptably high level.
An object of the present invention is to provide a carriage for an ink cartridge as a source of supply of ink to an ink-jet printhead for an ink-jet printer, wherein a lock lever applies a sufficiently large force to the ink cartridge with less effort required for releasing the lock lever.